Preparation of soap-salt complexes



United States Patent M PREPARATION OF SOAP-SALT COMPLEXES UTILIZINGPREFORMED ACID SALT No Drawing. Application July 20, 1954, Serial No.444,665

11 Claims. (Cl. 252-39) This invention relates to grease compositionsand more particularly relates to lubricating grease compositionscontaining complex soap-salt thickeners. Still more particularly, thisinvention relates to a method of preparing such greases wherein apreformed acid salt is employed as the salt-forming portion of thethickener and to grease compositions so formed. The method of thisinvention is especially useful in the preparation of lubricating greasecompositions containing complex soap-salt thickeners in which there is ahigh ratio of salt to soap on a mole basis.

Soap-salt complexes are well known in the art for thickening lubricatingoils to produce lubricating grease compositions. These complexthickeners have been employed for high temperature greases and consistof combinations of metal salts of low molecular weight carboxylic acidswith metal soaps of high molecular weight fatty acids. Normally thesoaps and salts have been employed in proportions in the range of about0.5 to 3 moles of salt per mole of soap. Because the thickening elfectof the salt is rather low, it has been generally considered desirable tomaintain the mole ratio of salt to soap below about 3 since above a moleratio of about 3 the total requirement of soap-salt thickener needed tomake greases of satisfactory penetration characteristics was found to bequite high.

However, recently it has been found that by drastically increasing thesalt content and with it the metal content of soap-salt complexes,entirely new properties may be built into these complexes which greatlyincrease their value as grease thickeners. More specifically, it hasbeen found that complexes of metal salts of low molecular weightcarboxylic acids with metal soaps of high molecular weight carboxylicacids which contain at least 7 moles and up to as much as 40 moles ormore, preferably about 8 to 25 moles, of the low molecular weight acidper mole of the high molecular weight acid have outstandingload-carrying, dispersant, and various other beneficial characteristicsin addition to thickening properties comparable to soap-salt complexescontaining substantially lower proportions of low molecular weightcarboxylic acids. These particular thickeners and their utilization inlubricating grease compositions are described in detail in theco-pending Morway and Kolfenbach application Serial No. 387,527, filedOctober 21, 1953.

Because of the difiiculties encountered in handling large quantities ofthe low molecular weight acids and in particular acetic acid in themanufacture of these lubricating grease compositions which contain acomplex soap-salt thickener having a high salt to soap ratio, it wasrecognized in the aforementioned patent application that it would bedesirable to employ a preformed metal salt of the low molecular weightacid, such as calcium acetate, in the grease-making procedure in lieu ofthe direct use in the grease-making procedure of the low molecularweight acid itself. However, it was found that unsatisfactory greaseswere formed if the preformed metal salt 2,735,815 Patented Feb. 21, 1956of the complex soap-salt thickener. Thus it was not possible tocompletely eliminate the difficulties such as acid solidification,storage, pumping, etc, encountered with handling the low molecularweight acids such as acetic acid.

It has now been found in the case where acetic acid is employed as thelow molecular weight carboxylic acid that by employing an acid salt ofcalcium, barium, or strontium instead of the neutral acetate, it ispossible to produce excellent greases without the necessity of employingany free acetic acid in the grease-making procedure. Although it will beclearly understood that these preformed acid salts may be employed ingreases containing complexes having a salt to soap ratio below about 3,the method of this invention is especially useful in and is particularlydirected to the preparation of lubricating grease compositionscontaining complex soap-salt thickeners in which there is a high ratioof salt to soap on a mole basis. More particularly, the presentinvention is directed to lubricating grease compositions containing acomplex soap-salt thickener wherein the ratio of salt to soap on a molebasis is at least 7 and up to as much as 40 or more and preferably about8 to 25.

where M is an alkaline earth metal selected from the group consisting ofcalcium, barium, and strontium, and n is an integer of 1 to 3. The acidsalt is employed in the grease-making procedure in accordance with thisinvention in lieu of acetic acid and is used in combination with a highmolecular weight carboxylic acid to form a complex soap-salt thickener.The complex is formed by neutralizing the free acid portion of the acidsalt and the high molecular weight carboxylic acid with a basic reactingcompound of a metal which is preferably the same metal as that of theacid salt. The neutralization reaction is preferably carried out in atleast a portion of the lubricating oil which is to be thickened to agrease consistency by the complex soap-salt thickener. The mixture ofthe lubricating oil and neutralized acid salt and high molecular weightcarboxylic acid is heated to an elevated temperature, preferably in therange of about 450 to 550 F. or higher, to dehydrate the product and topromote formation of the complex. Theamount of the complex in the finallubricating grease composition may be in the range of about 5 to 30% byweight based on the total composition.

The acid salts may be conveniently prepared by reacting a hydroxide orcarbonate of calcium, barium, or strontium with approximately thestoichiometric proportions of acetic acid required to produce an acidsalt hav- Also, by way of example in the case of barium, about one moleof barium carbonate or barium hydroxide may be reacted with about 5moles of acetic acid to form an acid salt having the formula The acidsalts so formed are free-flowing powders 'or granules which may besimply and inexpensively stored and handled. When the metal hydroxide isemployed, the powdered acid salt contains all of the water of reaction.The reaction itself may be conveniently conducted at atmosphericconditions of temperature and pressure and is preferably carried outwith intimate mixing of the reactants. The time required for completionof the reaction is short and in view of the excess acid present isalmost instantaneous. The acid salt may also be conveniently prepared byadding the appropriate number of moles of the neutral acetate salt toacetic acid. For example, about 1 mole of neutral calcium acetate wouldbe added to about 1 mole of acetic acid to form an acid salt having theformula Ca (C2H302) 2 C2H402 The high molecular weight carboxylic acidsuseful for the purposes of the present invention are those having about12 to 30 carbon atoms and preferably those having about 16 to 22 carbonatoms per molecule. These acids may be derived from saturated orunsaturated naturally occurring or synthetic fatty materials. The fattyacids normally used in the manufacture of conventional greases,particularly the more saturated acids, are preferred. Examples of suchacids include stearic, hydroxy stearic, such as 12-hydroxy stearic,di-hydroxy stearic, poly-hydroxy stearic and other saturated hydroxyfatty acids, arachidic, hydrogenated fish oil and tallow acids, etc.However, unsaturated acids, such as oleic, ricinoleic and similar acidsmay likewise be used. It will be understood, of course, that thenaturally occurring or synthetic fatty materials mentioned above may bedirectly employed in the grease-making process to form soaps of highmolecular weight carboxylic acids by treatment thereof with the basicmetal reacting compound in the grease making process.

The lubricating oil employed to produce lubricating grease compositionsin the method of this invention may be mineral as well as syntheticlubricating oils. These synthetic oils include synthetic lubricatingoils having a viscosity of at least 30 SSU at 100 F. such as esters ofmonobasic acids (e. g. ester of Ca Oxo alcohol with Ca Oxo acid, esterof C13 Oxo alcohol with octanoic acid, etc.), esters of dibasic acids(e. g. di-2-ethyl hexyl sebacate, di-nonyl adipate, etc.), esters ofglycols (e. g. C13 Oxo acid diester of tetraethylene glycol, etc.),complex esters (e. g. the complex ester formed by reacting one mole ofsebacic acid with two moles of tetraethylene glycol and two moles of2-ethyl-hexanoic acid, complex ester formed by reacting one mole oftetraethylene glycol with two moles of sebacic acid and two moles of2-ethyl hexanol, complex ester formed by reacting together one mole ofazelaic acid, one mole of tetraethylene glycol, one mole of C8 Oxoalcohol, and one mole of C8 Oxo acid), esters of phosphoric acid (e. g.the ester formed by contacting three moles of the mono methyl ether ofethylene glycol with one mole of phosphorus oxychloride, etc.),halocarbon oils (e. g. the polymer of chlorotrifiuoroethylene containingtwelve recurring units of chlorotrifluoroethylene), alkyl silicates (e.g. methyl polysiloxanes, ethyl polysiloxanes, methyl-phenylpolysiloxanes ethylphenyl polysiloxanes, etc.), sulfite esters (e. g.ester formed by reacting one mole of sulfur oxychloride with two molesof the methyl ether of ethylene glycol, etc.), carbonates (e. g. thecarbonate formed by reacting Ca Oxo alcohol with ethyl carbonate to forma half ester and reacting this half ester with tetraethylene glycol),mercaptals (e. g. the mercaptal formed by reacting 2- ethyl hexylmercaptan with formaldehyde), formals (e. g. the formal formed byreacting C13 Oxo alcohol with formaldehyde), polyglycol type syntheticoils (e. g. the compounds formed by condensing butyl alcohol withfourteen units of propylene oxide, etc.), or mixtures of any of theabove in any proportions. Quite generally the mineral or synthetic oilshould have a viscosity within the range of about 35 to 200 SSU at 210F. and flash points of about 350 to 600 F. Lubricating oils having aviscosity index of 100 or higher may be employed. However, oils of lowerviscosity index such as below 60 VI give better yields. Complexsalt-soap proportions of 4 about 5 to 30 wt.% and preferably about 10 to20 wt. per cent pased on the total grease composition may be employed inpreparing grease compositions in accordance wtih the method of thisinvention.

The preferred grease-making procedure of this invention comprises theformation initially of a mixture of the acid salt, the high molecularweight carboxylic acid, and a basic reacting compound, such as thehydroxide, of a metal which is preferably the same as the metal in theacid salt in a portion or all of the lubricating oil which is to beutilized in the grease composition. Preferably at least one-third of thetotal lubricating oil is utilized in the preparation of this initialmixture. The free acid portion of the acid salt and the high molecularweight carboxylic acid are neutralized by the basic reacting compound. Asuflicient amount of the basic reacting compound is employed toaccomplish this neutralization. It will be understood that the term freeacid portion of the acid salt as used herein refers to the right handportion of the aforementioned formula, namely the group. The highmolecular weight carboxylic acids and the acid salt may be coneutralizedby adding the basic reacting compound to the oil mixture containing boththe acid salt and the high molecular weight carboxylic acid, or thecarboxylic acids may be neutralized in a stepwise procedure. If thestepwise procedure is employed the high molecular weight acid may beadded to the oil mixture containing the basic reacting compound first,followed by the addition of the acid salt. Thereafter the lubricatingoil containing the neutralized materials is heated to an elevatedtemperature preferably in the range of about 450 to 550 F. or higher todehydrate the product and to promote formation of the complex. Generallya period of heating in the range of about 10 to 30 minutes will besuitable to effect the formation of the complex. Thereafter thecomposition is cooled and the remainder of the lubricating oil is addedin the case where only a portion of the lubricating oil was initiallyemployed. It will be understood, however, that, if desired, the acidsalt and the high molecular weight carboxylic acid may be neutralizedtogether in a separate step and then added to the lubricating oil afterwhich the mixture is heated to an elevated temperature in the range ofabout 450 to 550 F. to promote formation of the complex. It will befurther understood that other conventional thickeners, anti-oxidants,corrosion inhibitors, tackiness agents, load-carrying compounds,viscosity index improvers, oiliness agents and the like may be addedprior, during or after the heating step as will be apparent to thoseskilled in the art.

The following example is presented to more specifically set forth thisinvention, but it will be understood that it is not intended that theexample limit the present invention in any way.

EXAMPLE Four greases, 1, 2, 3, and 4, were prepared from the materialslisted below. Greases 1, 2 and 3 were prepared by initially mixing theingredients, with the exception of the phenyl alpha-naphthylamine, inthe proportions indicated in a conventional grease mixer and heating themixture to about 500 F. In the case of greases l and 2, the free aceticacid was added after the mixture of the other components had reached atemperature of about F., whereupon heating was continued to 500 F.Thereafter greases 1, 2 and 3 were cooled to about 250 F. whileagitated. Then the phenyl alpha naphthylamine was added and the greaseswere further cooled to about 200 F., homogenized and packaged.

Grease 4 was prepared by adding in order to the lubricating oil whichwas contained in a conventional grease kettle, the lime, the Hydrofolacid, the hydrogenated castor oil and the acid calcium acetate. Theaddition of these ingredients required about 0.5 hour. The mixture wasthen heated over about a 3 hour period to a temperature of about 500 F.The grease mixture was then transferred to a water-jacketed coolingkettle. This transfer took about 0.5 hour during which time the greasehad cooled to about 400 F. The grease was then further cooled in thecooling kettle to about 250 F. over a period of time of about 2.5 hoursat which point the phenyl alpha naphthylamine was added. The grease wasthen further cooled to about 200 F., homogenized and packaged.

1 Hydrogenated fish oil acids corresponding to commercial stearic acidin degree of saturation.

2 8.0% glacial acetic acid+3.0% hydrated limc giving an acid salt of theformula Ca(CiHa02)z.C2l-I4Oz.

Properties Excellent Excel- Excel- Dnsatrs- Appearance and Structurelent lent factory I giluitggltllgl Dropping Point, F 500+ 500+ 500+Penetrations, 77 F. mm./l:

Unworked 60 Strokes- Worked 60 Str0kes Worked 75,000 Strok Worked100,000 Strokes..

Norma Hofiman Oxidation Hours to p. s. i. drop in Oxygen pressure (210F.) 245 254 260 (Spindle Test, 1,000 B. P. M.,

1 Incomplete dispersion of the salt resulting in soft semi-fluid grainygrease.

It will be noted that greases 1 and 2 which were prepared by employing asubstantial proportion of glacial :acetic acid in combination withneutral calcium acetate were excellent greases. However, when a grease(grease 13) was prepared without the utilization of any glacial aceticacid by employing solely neutral calcium acetate, an unsatisfactorygrease was produced. It will be noted, however, that grease 4 which wasprepared in accordance with this invention by employing solely the acidsalt of calcium acetate was an excellent grease and did not require theutilization of any glacial acetic acid in its preparation.

What is claimed is:

1. An improved method for preparing a lubricating grease compositioncontaining a grease-thickening proportion of a complex soap-saltthickener which comprises preforming an acid salt having the formulawhere M is an alkaline earth metal selected from the group consisting ofcalcium, barium and strontium and n is an integer of 1 to 3, forming amixture comprising a major proportion of a lubricating oil, a minorproportion of said acid salt, a minor proportion of a high molecularweight carboxylic acid and a basic reacting compound of a metal in anamount suflicient to neutralize said high molecular weight carboxylicacid and the free acid of said acid salt, heating the resultant mixtureat an elevated temperature until a soap-salt complex is formed and then.cooling to obtain said lubricating grease composition, the

6 proportions of said salt and said soap in said complex' being about0.5 to 40 mols of salt per mol of soap.

2. Method according to claim 1 wherein the proportionof said complexsoap-salt thickener in said grease composition is in the range of about5 to 30% by weight based on the total composition.

3. Method according to claim 2 wherein the proportions of salt and soapin said thickener are in the ratio of about 7-40 moles of salt per moleof soap.

4. Method according to claim 1 wherein said heating step is carried outin the range of about 450 to 500 F.

5. In a method of preparing a lubricating grease composition containingin the range of about 5 to 30% by weight of a complex soap-saltthickener, the proportions of salt and soap in said thickener being inthe ratio of about 740 moles of salt per mole of soap, wherein saidgrease composition is formed by neutralization of high molecular Weightcarboxylic acids with a basic reacting compound of an alkaline earthmetal in admixture with a major proportion of a lubricating oil bysubsequent heating of the mixture at an elevated temperature in therange of about 450 to 550 F. and then cooling to obtain said lubricatinggrease composition, the improvement which comprises incorporating intosaid grease composition a preformed acid salt having the formula where Mis an alkaline earth metal selected from the group consisting ofcalcium, barium and strontium and n is an integer of 1 to 3 as the saltforming portion of said complex soap-salt thickener.

6. An improved method for preparing a calcium base grease compositioncontaining a complex soap-salt thickener which comprises preforming anacid salt of calcium acetate, said salt having the formula Ca (C2H302) 2C2H4O forming a mixture comprising a major proportion of a minerallubricating oil, a minor proportion of said acid salt, a minorproportion of a carboxylic acid having in the range of 18 to 22 carbonatoms per molecule and sufficient calcium hydroxide to neutralize thefree acid of said acid salt and said carboxylic acid, and heating theresultant mixture at a temperature in the range of about 450 to 550 F.until a soap-salt complex is formed, and then cooling to obtain saidgrease composition, the proportion of said complex in said greasecomposition being in the range of about 10 to 20% by weight and theproportions of said salt and said soap in said complex being in theratio of about 825 moles of salt per mole of soap.

7. Method according to claim 6 wherein said carboxylic acid compriseshydrogenated fish oil acids.

8. A lubricating grease composition comprising a major proportion of alubricating oil and in the range of about 5 to 30% by weight, based onthe total composition of a complex soap-salt thickener, said thickenerhaving been formed by the neutralization of a high molecular weightcarboxylic acid and an acid salt having the formula where M is analkaline earth metal selected from the group consisting of calcium,barium and strontium and n is an integer of 1 to 3, with a basicreacting compound of said metal, said composition having been heated toan elevated temperature to form said complex and cooling the compositionto obtain said lubricating grease composition, the mol ratio of salt tosoap in said thickener being within the range of about 0.5 to 40.

9. Composition according to claim 8 wherein the mole ratio of salt tosoap in said thickener is in the range of about 0.5 to 3.

10. Composition according to claim 8 wherein the mole ratio of salt tosoap in said thickener is in the range of about 7 to 40.

11. A lubricating grease composition comprising a and a carboxylic acidhaving in the range of 18 to 22 carbon atoms, per molecule with calciumhydroxide, the

range of about 8 to 25, said composition having beenheated at atemperature in the range of about 450 to 550 F. for an extended periodof time to form said complex and then cooling to obtain said lubricatinggrease composition References Cited in the file of this patent Boner:Lubricating Greases. Pub. 1954 by Reinhold Publishing Corp., chapter 16,section 11, page 621, New

mole ratio of salt to s ojap in said thickener being in the 10 York,

1. AN IMPROVED METHOD FOR PREPARING A LUBRICATING GREASE COMPOSITIONCONTAINING A GREASE-THICKENING PROPORTION OF A COMPLEX SOAP-SALTTHICKENER WHICH COMPRISES PREFORMING AN ACID SALT HAVING THE FORMULA.